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I'm new to this site and most impressed with the help available. I have a question regarding removal of duplicate points which has been asked before. However the QGIS solutions suggested do not appear to work for me. I'm using QGIS 2.0.1.

I have a file of about 100 attributed features which I have brought over from MapInfo into QGIS. I've run the Vector\Geometry Tools\Check geometry validity which gives about 40 duplicate points/nodes. To remove duplicates I have run the MMQGIS plugin which doesn't remove any and also the Topology Checker plugin using "must not have duplicates" but which tells me it can't find any errors.

Other suggestions have been using Generaliser plugin (which I cannot find in the repository)and also the Delete Identical (does not appear in the Data Management tools). Other suggestions are GRASS which I’m not familiar with yet.

Any suggestions from the experts as to the best/easiest way of doing this, specifically in QGIS? Thanks

Update. The following are the steps: 1) Run Vector \ Geometry Tools\ Check geometry validity 2) Save a file with only these duplicate points 3) Select the layer with duplicates 4) Run MMQGIS\ Modify \ Delete duplicate geometries specifying the selected layer as source and a new file name for the "cleaned" layer 5) Run the geometry validity tool again on the “cleaned “ layer and get any captured duplicate points 6) Compare with original duplicates, no change

As regards an image, the only thing I get is about 40 points displaying where the duplicates are.

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  • Thanks Sorin, however when I selected layer and tried the "delete duplicate geometries" in mmqgis it didn't help.
    – DirkB
    Commented Feb 19, 2014 at 7:46
  • Tested on duplicate points and it's working well in mmqgis (mmqgis 2014.01.06 on QGIS 2.0). Could you edit your question to list the exact steps that you used, perhaps share a sample of your data?
    – Simbamangu
    Commented Feb 19, 2014 at 9:21
  • In this case, can you share with us your vector layer, for a test? You can upload it on dropbox.com, and publish here only the public link.
    – Sorin Călinică
    Commented Feb 19, 2014 at 11:05
  • Cheers Sorin, will do tomorrow once I sort out the process.
    – DirkB
    Commented Feb 19, 2014 at 11:19
  • Thinking about this a bit more. The issue may be the fact that I think of points on a polygon as points when they are actually nodes, as compared to points proper ie. a single point by itself, which is probably what the remove duplicate points is aimed at. Is there a remove duplicate nodes command? Although remove duplicate geometries bypasses that.
    – DirkB
    Commented Feb 20, 2014 at 8:11

1 Answer 1

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In the Processing/Toolbox, there are two scripts:

enter image description here

and Delete duplicate geometries works very well (better than MMQGIS).

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  • Thanks gene. Looks like you're using SAGA. Haven't used this before. I'm not sure how to configure this as the OS4GeoW install is supposed to install this automatically and configure appropriately. Not displaying in the plugin section (I do have GRASS though). The .exe is installed, just need to display this in QGIS. Had a quick look by firing up the .exe (2011 file) and found the remove duplicate points tool and opened up the file but may need to do a bit of playing around/familiarisation to get this to work. I think I will post a separate query on this. Another tool to use.
    – DirkB
    Commented Feb 20, 2014 at 0:29
  • See <gis.stackexchange.com/questions/87065/enabling-saga-in-qgis>
    – DirkB
    Commented Feb 20, 2014 at 8:18
  • Delete duplicate geometries don't need SAGA
    – gene
    Commented Feb 20, 2014 at 16:04

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